The invention relates to a method of suppressing water resonance in a magnetic proton resonance spectrum which is determined from resonance signals which are generated, using pulse sequences, in an object which is arranged in a steady magnetic field, the pulse sequences comprising an rf electromagnetic water suppression pulse which is followed, after a waiting period during which a longitudinal water magnetisation resonance signal reaches at least substantially an amplitude zero, by rf electromagnetic pulses for generating the resonance signal.
The invention also relates to a device for performing such a method, comprising means for subjecting the object to a steady magnetic field and to a sequence of an rf electromagnetic water suppression pulse and rf electromagnetic pulses in order to generate a resonance signal and means for detecting the resonance signal.
Such a method for suppressing water resonance in a magnetic proton resonance spectrum is described in an article "Water Eliminated Fourier Transform NMR spectroscopy", S. L. Patt and B. D. Sykes, The Journal of Chemical Physics, Vol. 56, No. 6, Mar. 15, 1972. Therein, water suppression in a magnetic resonance spectrum is achieved by rotating, using a frequency-selective inversion pulse around the spin resonance frequency of water, a nuclear magnetisation of an object situated in a steady uniform magnetic field through 180.degree. with respect to an equilibrium magnetisation in the field, and by subsequently waiting until a longitudinal water magnetisation which is thus obtained and which opposes the steady field has reached a value zero. At the instant at which the longitudinal water magnetisation is zero or at least small with respect to a water equilibrium magnetisation, an acquisition sequence is generated, for example a spin echo sequence, in order to obtain a resonance signal in which spin magnetisation of desired molecules is represented. The described method aims to minimise the water magnetisation at the instant at which an excitation pulse is applied to excite spin magnetisation of other molecules. The described method is susceptible to field inhomogeneities in the magnetic field associated with the rf electromagnetic pulses and is effective only if this field is very uniform; however, this is not the case, for example when use is made of surface coils.